Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders. The native heart valves (such as the aortic, pulmonary and mitral valves) serve critical functions in assuring the forward flow of an adequate supply of blood through the cardiovascular system. These heart valves can be rendered less effective by congenital, inflammatory or infectious conditions. Such damage to the valves can result in serious cardiovascular compromise or death. For many years the definitive treatment for such disorders was the surgical repair or replacement of the valve during open heart surgery, but such surgeries are prone to many complications. More recently a transvascular technique has been developed for introducing and implanting a prosthetic heart valve using a flexible catheter in a manner that is less invasive than open heart surgery.
In this technique, a prosthetic valve is mounted in a crimped state on the end portion of a flexible catheter and advanced through a blood vessel of the patient until the prosthetic valve reaches the implantation site. The prosthetic valve at the catheter tip is then expanded to its functional size at the site of the defective native valve such as by inflating a balloon on which the prosthetic valve is mounted. Alternatively, the prosthetic valve can have a resilient, self-expanding stent or frame that expands the prosthetic valve to its functional size when it is advanced from a delivery sheath at the distal end of the catheter.
A prosthetic valve that has a relatively large profile or diameter in the compressed state can inhibit the physician's ability to advance the prosthetic valve through the femoral artery or vein. More particularly, a smaller profile allows for treatment of a wider population of patients, with enhanced safety. Thus, a need exists for delivery devices that can minimize the overall crimp profile of the prosthetic valve for the delivery of the prosthetic valve through the patient's vasculature.
Relatively long delivery devices, such as used for transfemoral delivery of a prosthetic valve, can inhibit the physician's ability to position the prosthetic valve precisely at the desired implantation site because the forces applied to the handle at one end of the delivery device can cause unwanted movement of the prosthetic valve at the opposite end of the delivery device. Thus, a need exists for delivery devices that allow a physician to accurately control the positioning of the prosthetic valve at the desired implantation location.
When introducing a delivery device into the body, an introducer sheath typically is inserted first and then the delivery device is inserted through the introducer sheath and into the body. If the prosthetic valve is mounted on a balloon catheter, the prosthetic valve can contact the inner surface of the introducer sheath and may become dislodged from its preferred location on the balloon catheter, depending on the size of the crimped valve. Thus, a need exists for delivery devices that can better retain the crimped valve at its desired location on the balloon catheter as it is advanced through an introducer sheath.